Alkyl Vinyl Aryl Halides

The extra strength of the carbon halogen bond in aryl halides.

Alkyl vinyl aryl halides.

For this reason alkenyl halides with the formula rch chx are sometimes called vinyl halides. Formally this is ethylene h 2c ch 2 with one of the hydrogens substituted by a heteroatom. Step 1 of 3 if the halogen atom halo group is bonded to a single bonded carbon atom a sp3 hybridized carbon atom then it is known as an alkyl halide. If the halogen atom halo group is bonded to a double bonded carbon a sp2 hybridized carbon atom then it is known as vinyl halide.

There is an interaction between one of the lone pairs on the chlorine atom and the delocalized ring electrons and this strengthens the bond. With the exception of iodine these halogens have electronegativities significantly greater than carbon. The carbon chlorine bond in chlorobenzene is stronger than you might expect. A vinyl halide is clearly a species with a formula h 2c c x h in which a halide is directly bound to an olefinic bond.

Consequently this functional group is polarized so that the carbon is electrophilic and the halogen is nucleophilic as shown in the drawing below. S n 1 reactions are theoretically possible but not generally observed as the formation of the aryl cation is not energetically favourable. Benzylic halides allylic halides vinylic halides and aryl halides. An aryl halide has general formula c6h 5x in which an halide group x has substituted the aryl ring.

Unlike typical alkyl halides aryl halides do not participate in conventional s n 2 reactions as the backside attack required for an s n 2 reaction is impossible owing to the planar structure of the aryl group. The functional group of alkyl halides is a carbon halogen bond the common halogens being fluorine chlorine bromine and iodine.